Intra-fractional uncertainties in cone-beam CT based image-guided radiotherapy (IGRT) of pulmonary tumors.

PURPOSE: Intra-fractional variability of tumor position and breathing motion was evaluated in cone-beam CT (CB-CT) based image-guided radiotherapy (IGRT) of pulmonary tumors. MATERIALS AND METHODS: Twenty-four patients (27 lesions: prim. NSCLC n=6; metastases n=21) were treated with stereotactic body radiotherapy (SBRT) (one to eight fractions). Prior to every treatment fraction (n=66) and immediately after treatment a CB-CT was acquired. Patient motion, absolute drift and drift of the tumor relative to the bony anatomy were measured. Tumor motion was investigated based on the density distribution in the CB-CT. RESULTS: Absolute intra-fractional drift (3D vector) of the tumor position was 2.8 mm+/-1.6 mm (mean +/- SD), maximum 7.2 mm. Poor correlation between patient motion and absolute tumor drift was observed. Changes of the tumor position due to patient motion and due to drifts independently from the bony anatomy were of similar magnitude with 2.1 mm +/- 1.4 mm and 2.3 mm +/- 1.6 mm, respectively. No systematic increase or decrease of breathing motion was seen. The intra-fractional change of breathing motion was more than 2 mm and 3 mm in 39% and 16%, respectively. CONCLUSION: Intra-fractional tumor position and breathing motion were stable. In IGRT of pulmonary tumors we suggest an ITV-to-PTV margin of 5 mm to compensate intra-fractional changes.     

Treatment of Postmenopausal Osteoporosis

Osteoporosis is a skeletal disease characterized by low bone mass and microarchitectural deterioration with a resulting increase in bone fragility and hence susceptibility to fracture. Calcium and vitamin D are the most commonly used therapies for osteoporosis, although their efficacy in osteoporotic fracture prevention remains uncertain. Biphosphonates are the most frequently prescribed medication for treatment of osteoporosis and are often considered as first-line therapy for the treatment of osteoporosis. Currently, hormone replacement therapy is only approved by the Food and Drug Administration (FDA) for short-term treatment of severe postmenopausal symptoms with the lowest dose used for the shortest time. In view of its lack of effect on the prevention of nonvertebral fractures, the use of raloxifene should be limited to women with spinal osteoporosis. Most experts agree that it is preferable to treat osteoporosis with a more potent agent than calcitonin and manage the pain separately. Currently, the FDA recommends the use of parathyroid hormone for treatment of osteoporosis for a maximum of 2 years because of the concern of development of osteosarcoma. Drs. Gupta and Aronow have no real or apparent conflicts of interest relating to the subject under discussion.     

Management of Peripheral Arterial Disease of the Lower Extremities

Smoking should be stopped and hypertension, diabetes mellitus, dyslipidemia, and hypothyroidism treated in patients with peripheral arterial disease (PAD) of the lower extremities. Statins decrease the incidence of intermittent claudication and improve exercise duration until the onset of intermittent claudication in persons with PAD and hypercholesterolemia. Antiplatelet drugs such as aspirin or clopidogrel, especially clopidogrel, angiotensin-converting enzyme inhibitors, and statins should be given to all persons with PAD. Beta blockers should be given if coronary artery disease is present. Exercise rehabilitation programs and cilostazol increase exercise time until intermittent claudication develops. Chelation therapy should be avoided. Indications for lower extremity percutaneous transluminal angioplasty or bypass surgery are (1) incapacitating claudication in persons interfering with work or lifestyle, (2) limb salvage in persons with limb-threatening ischemia as manifested by rest pain, nonhealing ulcers, and/or infection or gangrene, and (3) vasculogenic impotence. Dr. Aronow has no real or apparent conflicts of interest relating to the subject under discussion.     

Dysfunctional attitudes,loneliness, and depression in college students

The role of dysfunctional attitudes in loneliness among college students was investigated. Subjects were 50 introductory psychology volunteers (20 male, 30 female) who completed measures of loneliness severity, depression, and dysfunctional attitudes. The results showed a strong predictive relationship between dysfunctional attitudes and loneliness even after level of depression was statistically controlled. Lonely college students' thinking is dominated by doubts about ability to find satisfying romantic relationships and fears of being rejected and hurt in an intimate pairing. Lonely individuals also experience much anxiety in interpersonal encounters and regard themselves as undesirable to others. Generally, a negative evaluation of self, especially in the social realm, is present. Implications of the results for treatment planning for lonely clients are discussed.     

Aortic Stenosis

Patients with aortic stenosis (AS) have an increased prevalence of coronary risk factors, coronary artery disease, and other atherosclerotic vascular disease and an increased incidence of coronary events and death. Statins may reduce the progression of AS. Angina pectoris, syncope or near syncope, and heart failure are the three classic manifestations of severe AS. Prolonged duration and late peaking of an aortic systolic ejection murmur best differentiate severe AS from mild AS on physical examination. Doppler echocardiography is used to diagnose the presence and severity of AS. Once symptoms develop, aortic valve replacement (AVR) should be performed in patients with severe or moderate AS. Warfarin should be administered indefinitely after AVR in patients with a mechanical aortic valve and in patients with a bioprosthetic aortic valve who have either atrial fibrillation, prior thromboembolism, left ventricular systolic dysfunction, or a hypercoagulable condition. Patients with a bioprosthetic aortic valve without any of these four risk factors should be treated with aspirin 75-100 mg daily.     

Association of ankle-brachial index with severity of angiographic coronary artery disease in patients with peripheral arterial disease and coronary artery disease

The ankle-brachial index (ABI) was correlated with the severity of coronary artery disease (CAD) in 273 patients, mean age 71 years, with peripheral arterial disease and angiographically obstructive CAD (> 50% occlusion). Of 155 patients with an ABI < 0.40, 130 (84%) had 3- or 4-vessel CAD, 17 (11%) had 2-vessel CAD and 8 (5%) had 1-vessel CAD. Of 80 patients with an ABI of 0.40-0.69, 37 (46%) had 3- or 4-vessel CAD, 33 (41%) had 2-vessel CAD and 10 (13%) had 1-vessel CAD. Of 38 patients with an ABI of 0.70-0.89, 10 (26%) had 3- or 4-vessel CAD, 16 (42%) had 2-vessel CAD and 12 (32%) had 1-vessel CAD. The lower the ABI, the higher the prevalence of 3- or 4-vessel CAD and the lower the prevalence of 1-vessel CAD.     

Dosimetric evaluation of intrafractional tumor motion by means of a robot driven phantom

Purpose: The aim of the work was to investigate the influence of intrafractional tumor motion to the accumulated (absorbed) dose. The accumulated dose was determined by means of calculations and measurements with a robot driven motion phantom.Methods: Different motion scenarios and compensation techniques were realized in a phantom study to investigate the influence of motion on image acquisition, dose calculation, and dose measurement. The influence of motion on the accumulated dose was calculated by employing two methods (a model based and a voxel based method).Results: Tumor motion resulted in a blurring of steep dose gradients and a reduction of dose at the periphery of the target. A systematic variation of motion parameters allowed the determination of the main influence parameters on the accumulated dose. The key parameters with the greatest influence on dose were the mean amplitude and the pattern of motion. Investigations on necessary safety margins to compensate for dose reduction have shown that smaller safety margins are sufficient, if the developed concept with optimized margins (OPT concept) was used instead of the standard internal target volume (ITV) concept. Both calculation methods were a reasonable approximation of the measured dose with the voxel based method being in better agreement with the measurements.Conclusions: Further evaluation of available systems and algorithms for dose accumulation are needed to create guidelines for the verification of the accumulated dose.